Method for producing corn stalk pulp and paper products from corn stalk pulp

ABSTRACT

A new method for making pulp out of agricultural residue includes harvesting certain portion of plant stalk. The harvested plant stalk is bailed, transported and stored. At the mill, the plant stalk is chopped and goes through pulping process. The pulp is used to make varieties of papers with or without blending other wood based pulp.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a process for separating aportion of a corn plants and producing pulp from the plant for makingpaper products. More specifically, the present invention relates to amethod for harvesting portions of corn plants, that is, harvestingportions from the ground up to about the ears of the corn plant.Additionally, the present invention relates to a versatile pulpingprocess including at least one of mechanical, semi-chemical, andchemical process in order to produce pulp suitable for various paperproducts and producing various paper products from the pulp.

[0003] 2. Discussion of the Related Art

[0004] Trees provide a major source of the fiber supply for paper andpaperboard products industries. Softwood is a very suitable species formechanical pulping. Chemical pulps of softwood are used where thestrength of the paper product is important. Hardwood has a much shorterfiber than softwood and typically is not suitable for mechanicalpulping, but suitable for chemical and semi-chemical pulping. Hardwoodchemical pulp is used in paper products where surface smoothness andoptical properties are important. Wood based fiber is expensive as itincurs a high chemical charge for pulping, high energy input for cookingand refining, and high cost chemical recovery systems. Additionally, theenvironmental impact of wood based fiber is disadvantageous.

[0005] Agricultural residues such as cornstalks offer a promisingalternative source of fiber. In particular, they can serve as importantraw materials for making paper products, including products forprinting, writing, top linerboard, liner, tissue paper and otherspecialty grade paper. Additionally, environmental concerns haveheightened the interest in using agricultural fibers. Exploitation ofagro-based resources for making paper products is important to improvefarm profitability and reduce environmental pollution from burning andland disposal. Currently, the use of agricultural plants for makingpaper products is negligible. This is especially true in the UnitedStates where nearly 284 million tons of total agricultural residues,including 150 million tons of cornstalks are available annually.Cornstalk as a fiber source for papermaking is not popular in major pulpand paper producing countries as there are abundant and secure suppliesof pulpwood meeting the raw material requirements for large-scalecapital-intensive pulp mills. A large-scale pulp mill based onagricultural residues needs a large supply of bulky raw materials,thereby creating transportation problems. Additionally, agriculturalresidues are seasonal, thereby creating storage problems. Separation ofappropriate parts of cornstalk residue during harvesting will reducetransportation and storage problems. A pulp mill based on cornstalkshould be small scale and community based. Optionally, a large-scalemill may be used depending on the availability of cornstalk and supplylogistic.

[0006] The related art covering non-wood pulping and papermaking includeU.S. Pat. No. 6,302,997 issued to Hurter et al. This describes methodsof non-wood pulping for papermaking. Cornstover (stalks, leaves andhusks) are used in this process and contain low quality fiber and a highquantity of debris. Accordingly, transport and storage problems in thefarm as well as in the mill are present in the related art.Additionally, pith, leaves, and husk contain a small quantity of goodfibers. Therefore, tube grinders, conveyers, hydrapulpers, pumps,magnetic separators, and dewatering screens have to handle huge volumesof unnecessary materials.

[0007] Accordingly, there is a pulp yield of 39.6%, which issubstantially low due to the presence of large quantity of low qualityfiber that are mostly removed during downstream processing. This lowquality fiber consumes chemicals without giving any benefit to the pulpqualitatively and quantitatively and the mill faces huge disposalproblems due to large quantity of rejects. The related art uses thetraditional alkaline digestion process. The addition of an acidtreatment step, ozone bleaching step and a peroxide-bleaching step makesthis process expensive and complicated. The process also includes highdoses of chemicals during hydrogen peroxide bleaching. Despite thedisclosure of interesting process steps in the foregoing U.S. patent,the invention has a number of drawbacks, for example: 1) dealing withcornstover having materials such as pith, leaves and husk that have verylittle fiber value; 2) carrying the unnecessary mass to the mill createstransportation and storage and disposal problems of the large supply ofreject materials; 3) low pulp yield; 4) high chemical consumption inacid stage, bleaching stage and in adjustments of pH; 5) the processinvolves extra steps that increases capital costs and operatingexpenses; and 6) the process saves energy during alkaline cooking butconsumes more energy through refining.

[0008] The present invention focuses on non-wood paper making having anadvantageous approach. By establishing harvesting, pressing and bailingprocesses on the farm and allowing for gathering places of goods andstorage. Alternatively, it is to establish a mini mill at the center ofthe corn growing area where farmers will have their own storage facilityand will transport the materials to the mill at a schedule set by themill. Ideally, mill storage should not be more than about 15 days inorder to optimize the mill spatially. The mill should use a simple andenvironmentally benign process with low capital and operating costs tocompete with the larger wood based mills. These processes are notcurrently available in the art.

SUMMARY OF THE INVENTION

[0009] Accordingly, the present invention is directed to a process forproducing pulp and paper products from pulp that substantially obviatesone or more of the problems due to limitations and disadvantages of therelated art. For example, a process for producing pulps suitable for usein papermaking, top white liner making, liner making and other specialtypapermaking. The process includes a harvesting process for separatingportions of the cornstalk that are most suitable as fiber source in thefield, digesting the selected cornstalk portions with an alkalinepulping solution with or without the presence of anthraquinone and/orother catalysts, and treating the pulp with elemental chlorine freebleaching solution in order to produce bleached pulp suitable forpapermaking. An advantage of the present invention is to provide acornstalk harvesting process that will take the bottom portion of thecornstalk plant below about the ears of the plant, which contains mostlythe good fiber and less pith and leaving behind the rest of the plant inthe field for traditional farm use.

[0010] Another advantage of the present invention is to chop theselected cornstalk section using a modified wood chipper.

[0011] Another advantage of the present invention is to separate thechopped leaves and piths from the chopped stem pneumatically.

[0012] Another advantage of the present invention is to reduce thecornstalk processing steps from harvesting to digestion.

[0013] Another advantage of the present invention is to accept up to 15%of pith in the digester to simplify the separation process.

[0014] Another advantage of the present invention is to provide acornstalk pulping process that requires a minimum number of processingsteps. Another advantage of the present invention is to provide acornstalk pulping process that is cost effective and environmentallybenign at small- to medium-scale level.

[0015] Another advantage of the present invention is to provide acornstalk harvesting and pulping process that uses a minimal amount ofreadily available and inexpensive equipment.

[0016] Another advantage of the present invention is to provide acornstalk processing system during harvesting to separate the bottomportion of the cornstalk plant, below about the ears of the cornstalkplant, from the rest of the plant, which is still available to thefarmer for traditional farm use.

[0017] Another advantage of the present invention is to make compactsquare bales of dried cornstalk during the harvesting process to reducebulk to avoid transport and storage problem.

[0018] Another advantage of the present invention is to develop amanagement system for transportation and storage of selected cornstalk

[0019] Another advantage of present invention is to transport cornstalkfrom the collecting point to the mill.

[0020] Another advantage of the present invention is to leave portionsof the cornstalk plant rejected during harvesting in the field for soilconditioning and other traditional farm uses.

[0021] Another advantage of the present invention is to reduce thecontaminants in cornstalk during harvesting and compact baling processesin order to reduce hot water requirements in washing stage beforechemical impregnation and digestion steps.

[0022] Another advantage of the present invention is to chop thecornstalk followed by hot water washing and compression in screw feederwhere impregnated with cooking chemical before entering into thedigester.

[0023] In yet another advantage of the present invention is to apply acompression step to eliminate water and hot water-soluble extractivefrom the materials, and also to increase the digester intake.

[0024] A further advantage of the present invention is to add cookingchemicals just after the compression step for better chemicalimpregnation of de-structured raw materials in a continuous digester.

[0025] Another advantage of the present invention is to apply acompression step to increase the digester input and to increase theliquor impregnation into the material.

[0026] Another advantage of the present invention is to use the standardpaper mill equipment to process the cooked fiber.

[0027] Another advantage of the present invention is to digest the rawmaterials at low temperatures in the range of about 110 to 160° C. witha retention time of about 30 to 180 minutes.

[0028] Another advantage of the present invention is to add apretreatment step just after the washing and compression step, wherecellulose protecting agents such as MgCl₂ or MgCO₃, and the like, willbe impregnated at a temperature in the range of about 60 to 100° C. fora period of time in the range of about 30 to 60 minutes.

[0029] Another advantage of present invention is to maximize thehemicelluloses content of cornstalk chemical pulp by introducing apre-impregnation stage using cellulose protecting agents.

[0030] Another advantage of present invention is to take benefit ofhemicelluloses content in cornstalk pulp in papermaking process byblending with softwood kraft pulp and using wet end chemistry.

[0031] Another advantage of present invention is to find the synergiceffect of cornstalk pulp in a typical papermaking/boardmaking furnish.

[0032] Another advantage of the present invention is to use lesschemicals, for example, 8 to 20% active alkali with or without thepresence of catalyst such as anthraquinone and the like.

[0033] Another advantage of the present invention is to use lesschemicals in the elemental chlorine-free bleaching process.

[0034] Another advantage of the present invention is to apply chlorinedioxide, alkaline extraction, peroxide, ozone, and oxygen bleachingstages to obtain about 80 to 95% of brightness.

[0035] Another advantage of the present invention is to avoid sulfurbased chemicals in cooking liquor or in bleaching liquor to remaincommitted to environmentally benign pulping and bleaching processes.

[0036] Another advantage of the present invention is to fractionate thefiber after bleaching into long fibers (mainly from cornstalk skin) andinto short fibers (mostly from pith). Another advantage of the presentinvention is to use the cornstalk pulp to produce various grades ofpaper without even fiber fractionation into long and short fiberfraction.

[0037] Another advantage of the present invention is the flexibility ofusing chemical pulp in a blend with bleached soft wood kraft pulp (withor without prior refining) and filler.

[0038] Another advantage of the present invention is that the long fiberfractions will be refined to approximately 250-500 ml CSF and then addedto the short fiber fraction before papermaking step.

[0039] Another advantage of the present invention is a cornstalk pulpingprocess that minimizes water use by reducing the number of washingstages and by minimizing the number of dilution and thickening stages,by recycling the internal water as much as possible.

[0040] Another advantage of the present invention is to improve thepaper quality made from the bleached cornstalk pulp by adding bleachedsoftwood kraft pulp approximately 5 to 20%, inorganic fillerapproximately 5 to 60%, starch approximately 0.25 to 4%, sizing agentapproximately 0.025 to 0.5%, cationic, anionic and/or amphotericretention aids, and the like.

[0041] Another advantage of the present invention is to use cornstalkchemical pulp with or without refining in a blend with bleached softwoodkraft (with or without prior refining) and filler.

[0042] Another advantage of the present invention is to use the bleachedcornstalk chemical pulp in a blend with bleached softwood kraft pulp,bleached hardwood chemical pulp and filler.

[0043] Another advantage of the present invention is to use the bleachedcornstalk chemical pulp in a blend with hardwood CTMP (chemi-thermomechanical pulp) and/or BCTMP (bleached chemi-thermo mechanical pulp)and filler.

[0044] Another advantage of the present invention is to use the bleachedcornstalk chemical pulp in a blend with bleached cornstalk chemi-thermomechanical pulp (CTMP/BCTMP), bleached hardwood mechanical pulp,bleached softwood kraft pulp and filler.

[0045] Another advantage of the present invention is to use the bleachedcornstalk mechanical pulp in a blend with hardwood chemical pulp and/orbleached hardwood mechanical pulp, bleached softwood kraft pulp andfiller.

[0046] Another advantage of the present invention is to use unbleachedcornstalk chemical and/or semi-chemical pulp in a blend with unbleachedsoftwood kraft pulp and/or unbleached softwood semi-chemical (kraft)pulp to prepare packaging grade paper.

[0047] Another advantage of the present invention is to apply thebleached cornstalk chemical pulp in a blend with bleached softwood kraftpulp (0 to 10%) and filler (10 to 60%) in the outer layer of the multilayer papers. The inner layer of the paper may contain inferior qualityfibers, such as recycled fiber, inferior virgin fiber, pulp havingextractives and pulp unsuitable for exposure on paper surface.

[0048] Another advantage of the present invention is to use the bleachedcornstalk chemical pulp in top liner by blending with bleached softwoodkraft pulp (0 to 10%) and filler (0 to 60%) along with very smallquantities of starch, sizing agents and retention aid.

[0049] Another advantage of the present invention is to use the bleachedcornstalk chemical pulp in an existing mill using the furnish consistedof hardwood and softwood pulp and filler in order to enhance the paperstrength properties through superior fiber bonding capability ofcornstalk pulp.

[0050] Another advantage of the present invention is to use the bleachedcornstalk chemical pulp to increase the filler retention in the paperwithout compromising strength properties.

[0051] Another advantage of the present invention is to use theunbleached cornstalk chemical pulp with unbleached chemical or semichemical softwood kraft pulp to enhance strength properties of paperssuch as sack paper, packaging paper etc.

[0052] Additional features and advantages of the invention will be setforth in the description which follows, and in part will be apparentfrom the description, or may be learned by practice of the invention.The objectives and other advantages of the invention will be realizedand attained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and together with the description serve to explain theprinciples of the invention.

[0054]FIG. 1 is a flow chart describing a chemical pulping process forcorn stalk pulp.

[0055]FIG. 2 is a flow chart describing a mechanical pulping and highyield pulping process for corn stalk pulp.

[0056]FIG. 3 is a flow chart describing a paper making process from cornstalk pulp.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0057] Today the paper industry in the United States is in the samesituation as steel industry was a few decades ago. Small-scale modernsteel industries are more efficient than large-scale facilities.Accordingly, it is time to look for technology for the development ofsmall-scale efficient pulp and paper industry. It is also time to lookfor inexpensive fiber sources to face the competition from high yieldplantation trees such as eucalyptus, acacia, and the like. Agriculturalresidue such as cornstover can compete with eucalyptus and acacia as aninexpensive source of fiber. The potential worldwide supply ofcornstover is approximately over 750 million tons per year, and theUnited States alone can provide approximately 150 million tons annually.

[0058] The present invention emphasizes the need of the paper industryto move to mini mill processes and to use agricultural residues, such ascorn stalks, and the like as fiber sources. The process is a combinationof compression impregnation and chemical processes to produce highquality pulps.

[0059] The term agricultural residue is used to identify the materialremaining at the farm after separating the main crop from the plant. Forexample, cornstalk is an agricultural residue, as it remains in thefield after harvesting the main product corn. The residual cornstalk hasvery little or no commercial value at present. Of course, otheragricultural residues may also be utilized and have been contemplated.

[0060] The present invention provides a cost effective andenvironmentally benign process. For example, one stage of compressionimpregnation and pulping and three to seven subsequent stages ofbleaching convert the selected part of cornstalk into high quality,bright papermaking pulps of excellent strength, cleanliness, anddrainage rate. The process utilizes a portion of the cornstalk plantbelow about the ears, for example, approximately the bottom 2 to 3 ft ofcornstalk plant (without leaves and husk). These portions contain up toapproximately 15% pith without using any type of mechanical or chemicalde-pithing, thereby producing pulps having strength properties that aresimilar and/or superior to the properties of hardwood pulps in lab-scaletrial. Additionally, a total pulp yield of about 46-50% may be achievedon selected cornstalk portions, which is equal to or better than thetotal yield value of hardwood pulps. The hardwood pulp process utilizesharsher pulping conditions and more costly pulping and bleachingprocesses. The processing of the present invention establishes a highyield using low chemical charges, temperature, and pressure.

[0061] Cornstalk Process Stages

[0062] The process of the present invention includes a unique harvestingprocess that separates portions of the cornstalk plant, that is portionsfrom the ground up to about the ears of the plant. For example, theportion separated may be approximately the bottom 2 to 3 ft of cornstalkplant. Of course, this depends on the characteristics of the plant. Theseparated cornstalk portions are compacted into a bale. For example,they are compacted into a square or rectangular bales and stored at thefarm until a predetermined time, when it is then transported to themill.

[0063] The use of whole cornstalks including leaves and husk in pulpinggives low yield and consumes more chemicals without any real benefit.

[0064] A compression impregnation step that is common inchemi-thermo-mechanical pulp, but never used in chemical pulping hasbeen used for different purposes.

[0065] The alkaline pulping step used in the present invention inpulping is milder than that used in hard wood pulping process. Thepulping step uses both batch and continuous processes. For example, aPandia type continuous digester is suitable for alkaline pulping ofcornstalk. Pulp from the digester contains low lignin, for example,kappa 8 to 10. Additionally, the pulp can be bleached to a highbrightness by using fewer steps than hardwood pulp process and obtaininga similar yield.

[0066] The processes of the present invention may be done in thefollowing order; however, variations from the order have also beencontemplated.

[0067] Cornstalk Harvesting, Storage, and Transportation

[0068] In this process, the harvester removes a portion of the cornstalkplant. For example, the harvester cuts the cornstalk just below theears. The first cut may be used for soil conditioning, animal beddingand other traditional farm uses. The second cut removes a portion of thecornstalk plant below about the ears of the cornstalk plant. Thisportion has moisture content of about 10 to 20% and is compacted into abale. Typically, it is compacted into a rectangular bale or square bale,which is then transported to a storage facility. The bale is stored in adry atmosphere in order to avoid fungi and the like.

[0069] Each farmer in approximately 50 mile radius relative to the pulpmill stores the compact bales on the farm until a predetermined time fordelivering the materials to the mill. This allows the mill to keep aninventory of compact bales for a reduced time, for example, about 2weeks. Of course the time of storage of the bales may be longer orshorter. This type of management will reduce storage requirements at themill site. The mill may pay the farmers for storage time or some otherform of contractual relationship may be established with the farmers.

[0070] Processing of Raw Materials

[0071] The next step in the process is to arrange the raw materials intoa digester. In this process the compacted bales of cornstalk portionswill be loosened and chopped to approximately 25 to 40 mm size. Thechopped material is arranged, for example dumped, onto a lower part ofan inclined conveyer belt. The conveyer belt may be fitted in a steelhousing filled with hot water under constant circulation. The conveyerwill transport the cornstalk within the liquid from one end of theconveyer to the other end of the conveyer. This is the process ofwetting the cornstalk. In this process dirt and/or other foreignmaterials attached to cornstalk portions are loosened and separated viahot water soluble materials into the water media. The upper end of theconveyer may be slightly inclined and another conveyer may be fitted ina steel housing and having an incline of about 30 degrees. The conveyorbelt leads to a hopper. However, the configuration of the belt may be inany suitable configuration leading to the hopper. For example, theincline may be less than or greater than 30 degrees. In-situ cleaningprocess is performed on the cornstalk as it is transported along theconveyor belt. For example, continuous hot water is sprayed onto thematerial being transported along the conveyor belt to clean off theresidual dirt and any other foreign material. At the opposite end of theconveyor belt the cleaned material, which may be saturated with hotwater, is arranged into the hopper. The material may be fed into thehopper with a plug screw feeder or any other suitable technique.

[0072] Pulping Process

[0073] The plug screw feeder compresses the cornstalk coming from thefeeder and removes the excess water and hot water soluble extracts. Atthe end of the screw feeder, the compressed cornstalk comes in contactwith cooking liquor, thereby providing better penetration of cookingliquor as it enters into the digester. In this zone the cooking liquorflow is controlled in order to have liquor to cornstalk ratio of about3:1 to 7:1.

[0074] In case of pretreatment with cellulose protecting agents, anadditional step before the addition of cooking liquor should be added tothe pulping process.

[0075] A variety of different digesters may be used, for example, aPandia digester and the like. The Pandia digester is a horizontalcontinuous digester that is well suited for the production of pulp fromall different non-wood fiber raw materials and provides excellentresults for high yield processing.

[0076] When using a continuous Pandia digester it may contain two tothree horizontal tubes. The temperature may be raised to about 120 to170° C. at the end of first tube and about 120 to 170° C. in the secondtube for continuing the cooking, and in the third tube to about 100 to110° C. for cooling down, before letting it blow to the blow tank. Theramp time in the first horizontal tube may vary from about 20 to 40minutes, the cooking time at the second tube may vary from about 20 to90 minutes, and cooling time in the third horizontal tube may vary fromabout 10 to 15 minutes. Optionally, the blow tank may include anagitator fitted to defibrate the cooked fiber in a hot spent liquormedia.

[0077] In a batch process, a plug screw feeder compacts the bulkycornstalk to allow for a maximum load. The load fills a rotating and/orstationary digester with a liquor to solid content of about 3:1 to 7:1.The cooking temperature varies from about 120 to 170° C. for a periodbetween about 30 to 120 minutes. The ramp time for raising thetemperature from feed temperature to cooking temperature varies fromabout 15 to 60 minutes. After the cooking, the temperature of thedigester is lowered to about 100 to 110° C. and the pulp is released toa blow tank. In the blow tank, an agitator is fitted to defibrate thecooked fiber in hot spent liquor media.

[0078] The cooking liquor includes about 2 to 20% active alkali. About12 to 15% active alkali (on oven dry cornstalk basis) cooking solutionmay be used to obtain a bleachable grade cornstalk pulp of yield rangeof about 45 to 50%. To obtain liner pulp at the yield range of about 60to 70%, the active alkalinity may be in the range of about 6 to 10%, andto obtain corrugating medium at the yield range of about 80 to 95%, theactive alkalinity may be in the range of about 2 to 4%. The cookingliquor may contain any combination of catalytic anthraquinone, and/orother similar reagents.

[0079] Fiber Processing Step

[0080] For chemical pulps the agitator that may be fitted at the bottomaccomplishes defibration in the presence of hot liquor. Defibratingseparates the fiber for thorough pulp washing and the fibers might needto be further refined for papermaking. The chemical pulps especially forhigh yield chemical pulp, that is yields of about 60 to 70%, are refinedafter the cooking process to liberate the individual fibers. Forultra-high yield pulp of about 80 to 95% obtained for corrugatingmedium, the pulps are refined to separate the individual fibers.

[0081] Screening, Washing and Cleaning Stage

[0082] After disintegration in a blow tank, pulps will be sent through acoarse screen to remove uncooked and/or semi-cooked and/or fiber lumpsbefore sending the pulp to washing stage. Black liquor will be separatedat screening and washing stages and sent to a chemical recovery boilerfor recycling. The chemical pulps require thorough washing in order torecover processing chemicals and to clean the pulp. The brown stock canbe washed by the existing commercial washer. Screening and cleaning ofcornstalk pulp are preferably done before bleaching. This will savebleaching chemicals and improve the bleachability of the pulp.

[0083] Bleaching

[0084] A moderate application of bleaching solution, for example,chlorine dioxide, alkaline hydrogen peroxide, and alkaline extractionsolutions may be used to remove the residual lignin and to increase thepulp brightness to a predetermined level. Bleaching conditions such astemperature, time, and bleaching liquor concentration, typically dependson lignin content of the pulp and on the optimum conditions forparticular bleaching agents.

[0085] For example, temperatures ranging from about 60 to about 90° C.are used when using chlorine dioxide or alkaline peroxide as a bleachingagent in a closed system. Typically, the bleaching processes last about30 to 120 minutes, which includes the time required to adjust the pulptemperature to the desired temperature level. The bleaching temperatureis maintained for about 30 to 120 minutes. A three step bleachingsequence (hereinafter “DED”) can raise the cornstalk pulps' brightnessto about 80 to 85% ISO level and addition of one of more bleachingstages such as peroxide, ozone, or oxygen bleaching stage can raise thebrightness to about 86 to 95% ISO.

[0086] Papermaking

[0087] The bleached pulp is a mixture of long fiber mainly derived fromcornstalk skin and short fiber derived mainly from pith. Refining ofthis mixture before papermaking will create more fines resulting in awater drainage problem because the fines hold more water than the fiber.

[0088] Short fiber does not need refining, whereas the long fibers mightor might not need refining in order to develop bonding properties. Thebleached fiber should be fractionated into long and short fiberfractions. The long fiber fraction will be refined and then mixed withthe short fiber fraction before papermaking.

[0089] In an alternative way, when the bleached cornstalk pulp is mixedwith bleached softwood kraft and/or bleached hardwood kraft pulp forpapermaking, the fractionation is not necessary. Since the cornstalkpulp is softer, slender and require less energy to refine, mechanicalaction during mixing with softwood kraft pulp and/or hardwood kraft pulplead to refining in some extent and develop fiber-fiber bondingproperties. Depending on the end products, cornstalk pulp (bleached orunbleached) can be mixed with softwood kraft pulp (bleached orunbleached with or without refining) to various extent.

[0090] The bleached pulp is used to prepare paper, for example, printingand writing paper, photocopy paper, top white linerboard, tissue paper,base paper, wood free papers, coated paper, multiplayer paper/paperboard, specialty papers, and the like. CTMP and BCTMP of cornstalk canbe used to prepare newsprint by blending with softwood kraft pulp (5 to20%). Bleached cornstalk CTMP can be blended with cornstalk bleachedchemical pulp for preparing writing & printing grade paper. The highyield semi-chemical cornstalk paper can be blended with high yieldsoftwood kraft pulp to produce sack paper, wrapping paper, packagingboard, carton board etc. Dissolving pulp and useful by-products derivedfrom hemicellulose can be produced from cornstalk.

[0091] Printing and writing paper, photocopy paper, and top whitelinerboard may contain approximately 5 to 20% bleached softwood Kraftpulp, having approximately 5 to 60% filler content. The filler mayinclude any combination of calcium carbonate, clay, talc, kaolin,titanium dioxide, and the like. In addition to filler, any combinationof sizing agents, dry strength agents, wet strength resins, andretention aids may be applied during the paper making. The sizing agentsmay include any combination of rosin emulsion, alkenyl succinicanhydride (ASA), alkyl ketene dimmer (AKD), and the like. The drystrength agents may include any combination of starch, gums, solublecellulose derivatives, and the like. The wet strength resins may includeany combination of polyvinyl alcohol, latex, and the like. The retentionaid may include any combination of polyacrylamide, polyethylene amine,and the like.

EXAMPLES

[0092] The examples presented below illustrate cornstalk pulp and paperquality compared to hardwood pulp. Certain aspects of the examples aredescribed in terms of techniques and procedures found by the inventorsto work well in the practice of invention. The examples are createdthrough the use of standard laboratory practices of inventors. Theexamples presented are not meant to be limiting, and numerous changes,modifications or alterations may be applied without departing from thescope of the invention.

Example 1

[0093] The cornstalk portions were separated manually from the leavesand other unwanted materials. The cornstalk stems were then broken intosmall pieces mechanically. The mechanical separation was accomplishedwith two oppositely rotating devil teeth plates. The system separatesthe skin, however, a substantial quantity of pith remains with the skin.It is noted that any other suitable mechanical separating tool may beutilized.

[0094] Pulping experiments were conducted using the pith and skin asreceived from the process. The quantity of pith was about 23% of totalcornstalk except leaves, cones and ears. In a few laboratory scaleexperiments, the cornstalk skin was separated completely, and in somecases 15% pith was added to the skin to verify the effects of pith onhandsheet properties. In the experiments, the cornstalk pieces werecleaned in a pulper by using hot water and dried in air to obtain thedesired cornstalk consistency. The consistency of the cleaned cornstalkis beneficial in order to adjust the quantity of cooking chemicals,liquor to cornstalk ratio, and to know the pulp yield.

[0095] In this series of experiment, a ramp time of approximately 60minutes was applied, the cooking time was approximately 60 minutes, andcooking temperature was about 150° C. The cooking was done using a sodaprocess. The quantity of sodium hydroxide expressed as active alkali wasvaried from about 12 to 15% to get acceptable pulps. Tables 1, 2, and 3show the quantity of active alkali in cooking liquor, screened pulpyield, pulp freeness (CSF), and mechanical and optical properties ofhandsheets. TABLE 1 Handsheet properties of screened pulp from cornstalkwithout pith refined with PFI mill. Active Yield Tensile Tear IndexBurst index alkali Screen PFI CSF Density index (mN · (kPa · BrightnessOpacity Exp.. No. (%) (%) revolution (ml) (kg/m³) (N-m/g) m²/g) m²/g)(%) (%) CT-3 B1 13 45 2000 360 817 96 5.9 6.5 38 85 CT-3 B2 14 46 1500436 807 94 6.8 6.2 40 86 CT-3 B3 15 45 1500 370 830 96 6.2 6.5 40 86

[0096] TABLE 2 Handsheet properties of screened pulp from cornstalkcontaining approximately 15% pith refined with PFI mill Active YieldTensile Tear index Burst index Scattering alkali Screen PFI CSF DensityIndex (mN · (kPa · Brightness Opacity Coeff. Expt. No. (%) (%)revolution (ml) (kg/m³) (N-m/g) m²/g) m²/g) (%) (%) (m²/kg) CT-4 B1 1344 1300 360 847 90 6.5 5.9 39 83 15.6 CT-4 B2 14 45 1300 360 865 91 5.86.1 39 84 16.4 CT-4 B3 15 44 1300 370 845 91 5.9 6.0 38 83 15.0

[0097] TABLE 3 Handsheet properties of screened pulp from cornstalkcontaining approximately 23% pith unbeaten. Active Yield Tensile Tearindex Burst index Scattering alkali Screen PFI CSF Density Index (mN ·(kPa · Brightness Opacity Coeff. Expt. No. (%) (%) revolution (ml)(kg/m³) (N-m/g) m²/g) m²/g) (%) (%) (m²/kg) CT-2 B1 13 44 443 757 90 5.35.6 39 89 19.6 CT-2 B2 14 44 440 788 94 6.6 5.9 39 89 19.6 CT-2 B3 15 45467 786 93 6.0 5.8 40 89 19.8

[0098] The properties of pulps from cornstalk containing approximately15% pith are of a slightly lower quality than pulp properties obtainedfrom cornstalk without pith. The handsheet properties are close to thatof hardwood pulp. These results demonstrate that cornstalk containingcertain amount of pith is suitable to produce quality pulp. One caneasily avoid the huge task and cost associated with the mechanicalseparation of pith from the skin.) The existing process that could beused to separate skin from pith is hammer milling. This processgenerates lots of fines and dust, which will create environmentalpollution, deteriorate the fiber quality and increase the loss ofquality fiber. The development of new machine that will effectivelyseparate the skin in an environmentally begnin way and without cuttingand losing of good fiber will be very expensive. This separation ofcornstalk skin from pith is not necessary at all, as demonstrated inlab-scale experiments as shown in Table 1, 2 and 3. The kappa number ofthe pulps measured using Tappi Standard methods are between about 8 to12, which is very low compared to kraft softwood pulp (kappa number ofabout 27 to 30) and to hardwood pulp (kappa number of about 18 to 22)with a similar pulp yield. Accordingly, cornstalk pulp requires lessbleaching chemicals than half of those required for softwood andhardwood pulp.

Example 2

[0099] The raw cornstalk material, from the bottom portion of the plant,comprises mostly skin and includes knots and pith. That includes, thelower portion of the cornstalk plant below about the ears of the plant,for example, about the bottom 2 to 3 ft of cornstalk. This consists ofthick skin and relatively low pith. The leaves present in the lower partof cornstalk may be easily removed after chopping. The removal orseparation of the leaves may be done by blowing air due to thedifference in density of chopped cornstalk and leaves. The fiber qualityis not significantly affected due to the presence of a small quantity ofpith in the lower part of the cornstalk as shown in example 1.

[0100] In this experiment, 1.27 kg (oven dry basis) of selectedcornstalk, as described above, was cooked using about 14% active alkali.This was done with a liquor to cornstalk ratio of about 7:1, a cookingtemperature of about 150° C., a cooking time of about 60 min, and ramptime of about 60 min in order to raise the temperature from about 80 to150° C. The screened pulp yield was about 46%. The pulp was screened ona slot type screen of 0.008 inches and dewatered on a 200 mesh screen toremove the fines from the pulp. The pulp from this cook is shown as(CT-D1) and was subjected to bleachability tests. Two of the bleachedpulp samples were processed to prepare handsheet in order to determinethe mechanical and optical properties.

[0101] Six samples, of about 10 g each represented in the Table 4 belowas CT-d-1-1, CT-d-1-2, CT-d-1-3, CT-d-1-4, CT-d-1-5, CT-d-1-6. Thesesamples were bleached using a variety of chlorine dioxide concentrationsin the (D1) stage, followed by similar concentrations of sodiumhydroxide in an extraction stage (E), and similar concentrations ofchlorine dioxide in the (D2) stage. Additionally, three of the sixsamples were further bleached using a hydrogen peroxide (P) stage ofsimilar chemical composition in all three cases. The bleachingconditions, chemical concentrations, and chemicals used in the differentbleaching stages and the final brightness are presented in Table 4.TABLE 4 Bleaching conditions and resultant final brightness Sample No.CT-d-1-1 CT-d-1-2 CT-d-1-3 CT-d-1-4 CT-d-1-5 CT-d-1-6 D₁ Stage Kappafactor 0.20 0.25 0.30 0.35 0.35 0.30 Chlorine equivalent 1.6 2.0 2.4 2.82.8 2.4 Temperature (° C.) 90 90 90 90 90 90 Time (min) 90 90 90 90 9090 E₁ Stage NaOH (%) 2 2 2 2 2 2 Temperature (° C.) 90 90 90 90 90 90Time (min) 90 90 90 90 90 90 D₂ Stage Kappa factor 0.25 0.25 0.25 0.250.25 0.25 Chlorine equivalent 2.0 2.0 2.0 2.0 2.0 2.0 Temperature (° C.)90 90 90 90 90 90 Time (min) 90 90 90 90 90 90 P stage H₂O₂ (%) 2 — 2 2— — NaOH (%) 1.5 — 1.5 1.5 — — Na₂SiO₃ (%) 1.5 — 1.5 1.5 — — MgSO₄ (%)0.05 — 0.05 0.05 — — Final Brightness (%) 87.5 84 88 87 85 84

[0102] The results demonstrate that cornstalk pulp can obtain a highbrightness level while using low amounts of chemicals. The results aredue to lower lignin content of the pulp correspond to one third ofsoftwood and hardwood chemical pulps. The cornstalk needs less cookingchemicals, lower cooking temperatures and less cooking time compared tothe wood. The cornstalk processing cost will be similar to that woodwhen using a selected portion of the lower part of cornstalk.Additionally, the cost of storage and transportation will be minimizedby low cost of cornstalk, and ultimately the cost of cornstalk at themill gate will be much lower than that of wood.

[0103] Below is described about bleaching of cornstalk pulp onmechanical and optical properties of handsheets. TABLE 5 Properties ofbleached cornstalk pulp Tensile Tear index Burst index Scatt. CSFDensity Index (mN · (kPa · Brightness Opacity Coeff. Sample (ml) (kg/m³)(N-m/g) m²/g) m²/g) (%) (%) (m²/kg) CT-d1 (DED) 320 866 104 7.4 7.2 82.461 18.4 CT-d1 335 875 91 5.8 5.9 87.2 61 18.4 (DEDP)

[0104] The Canadian Standard freeness (CSF) of bleached cornstalk pulpswere in the range of about 540 ml. These CSF values came down to about330 ml by refining in PFI mill with only 1000 revolutions, which is lessthan one-tenth of those required for bleached eucalyptus (hardwood)chemical pulps. This indicates that cornstalk pulp has great advantagein terms of reduced refining energy consumption.

[0105] The addition of one peroxide step increased the brightness of thepulp from about 82.4 to 87.2%, but the strength properties of handsheetsdecrease significantly. As a result, it will be necessary to evaluatethe brightness requirement of final product in order to select thebleaching sequence and number of stages. For example, writing andprinting papers contain about 15 to 25% calcium carbonate as a filler toimprove paper surface smoothness, printing opacity, and brightness. Wetweb strength and dry strength of paper can be easily manipulated byusing wet end chemistry.

Example 3

[0106] In pilot-scale cooking, about 21.56 kg chopped cornstalks (ovendry basis) were packed in a rotating digester. A vacuum was created inthe digester allowing for better impregnation of the liquor (cookingsolution) into the cornstalk. The digester was rotated for about 30minutes, allowing the temperature to rise from ambient to about 80° C.for good impregnation. The ramp time was about 30 minutes to allow thetemperature to rise from about 80 to 150° C. and cooking time was about60 minutes at approximately 150° C. The cooking liquor includes about14% active alkali. At the end of the cooking period the pipeline betweenthe digester and blow tank was connected and the pressure was slowlyreleased to reduce the pressure corresponding to a temperature of about100 to 105° C. At this point the valve was opened completely to blow allof the pulp from the digester to the blow tank via the pressuredifferential. The blow tank includes a screen at the bottom tofacilitate washing the pulp with hot water after the transfer of thepulp to the blow tank. The pulp was washed with hot water and thentransferred to a large screen having 0.008 inches wide slots. The screenreject was less than about 0.07%. The pulp was then dewatered underpressure to about 30% solid content. The dewatered pulp was thenshredded and kept in a cold room for future use. The screened pulp yieldwas around 46.5%, which was similar to lab scale studies. Three samples,each of about 30 g on oven dry basis, were refined at 400, 700, and 1000revolutions in a PFI mill. Handsheets were prepared and tested accordingto TAPPI standard methods. Table 6 shows the results from the threesamples refined at 400, 700, and 1000 revolutions in PFI mill,respectively. TABLE 6 Physical, mechanical and optical properties ofscreened unbleached pulp from pilot scale pulping. Tensile Tear indexBurst index Scatt. CSF Density Elongation Index (mN · (kPa · BrightnessOpacity Coeff. Sample (ml) (kg/m³) (%) (N-m/g) m²/g) m²/g) (%) (%)(kg/m²) BD-2 (400) 380 674 3.00 83 4.2 5.7 27 95 BD-2 (700) 360 733 3.0282 4.5 5.4 30 93 BD-2 (1000) 350 728 3.10 81 4.5 5.5 27 94

[0107] The handsheet demonstrates very good mechanical properties withtensile index: 82 N-m/g, tear index 4.5 mN.m²/g, and burst index 5.5kPa.m²/g. It is important to note that during lab-scale pulping,cornstalks were washed well with hot water and pith contents wereadjusted manually. However, during the pilot scale trial we could notwash and adjust the pith content due to large amount of materialsinvolved. As a result, cornstalk used in pilot scale cooking mightcontain higher percentage of dirt and pith compared to cornstalk used inlab-scale cooking. This is one of the reasons of getting slightlyinferior pulp and low initial brightness compared to lab-scale pulp.These problems can be solved if pulp is produced at the pulp mill andincorporated with a full set of washing, screening and cleaning systems.

Example 4

[0108] In this example, properties of bleached cornstalk pulp werecompared to equivalently bleached kraft hardwood pulps. Moreover, twosets of copy paper with grammage of about 75 g/m² were prepared usingfiller, for example, precipitated calcium carbonate, starch, sizingagent, retention aids, etc, to see the properties. It is observed fromthe table that cornstalk pulp gives significantly higher tensile andburst index values than eucalyptus and aspen pulps. However, the tearvalues of eucalyptus are significantly higher than that of cornstalkpulp. The results are shown in Table 7. TABLE 7 Mechanical and opticalproperties of bleached cornstalk pulp and bleached kraft eucalyptuspulp, and bleached kraft aspen pulps. Tensile Tear index Burst indexScatt. CSF Density Elongation index (mN · (kPa · Brightness OpacityCoeff. Sample (ml) (kg/m³) (%) (N-m/g) m²/g) m²/g) (%) (%) (kg/m²) BD-2(DED) 350 680  3.2 81 4.5 5.7 82 61 BD-2 (DEDP) 355 820 2.58 82 4.364.93 82.9 65.2 21.1 BD-2(DEDP) 300 850 2.95 91.2 4.54 4.99 82.5 60.918.3 BD-2(DEDP), — 719 4.92 76.1 5.35 5.52 82.6 81.2 34.5 Filler: 6.6%BD-2(DEDP) — 640 3.24 62.6 5.66 4.08 85 86.8 48.1 Filler: 15.1%Eucalyptus 420 685 3.21 55.3 6.7 3.53 88 74 35.6 (bleached) Aspen 600 —— 35 4.4 1.93 82.5 78 (bleached)

[0109] These two experiments show that paper made from cornstalk pulpcan be improved significantly by judicial use of wet end chemistryduring papermaking. The opacity of handsheet, an important requirementfor printing and writing grade paper, was improved largely due to filler(precipitated calcium carbonate) integration in fiber matrix.

Example 5

[0110] In this example, physical, optical and mechanical properties ofpapers prepared in pilot scale paper machine from bleached cornstalkpulp and bleached mixed hardwood kraft pulp has been illustrated forcomparison. Pulping of cornstalk was carried out in pilot scale digesterand was subjected to washing, screening, dewatering and bleaching. Thebrightness of corn stalk pulp ranged from 88 to 90% as illustrated inexample 2.

[0111] The furnish for the preparation of cornstalk paper is as follows:Bleached cornstalk chemical pulp: 60%, Bleached northern softwood kraftpulp (commercial grade): 20%, filler (precipitated calcium carbonate):20%; starch: 0.5% (based on o.d. fiber basis); Hercon size 79 AKD(0.5%): 0.2% (o.d fiber basis) and Nalco 7520 Retention aid (0.1%):0.05% (o.d. fiber basis). Bleached cornstalk pulp (never dried) isblended with softwood kraft pulp in a hydrapulper. No refining wasrequired, as just agitation of hydrapulper dropped the freeness to about400 ml. Filler and starch are added to the machine chest. The sizingagent and retention aid are metered into the machine chest.

[0112] The furnish for the preparation of hardwood paper is as follows:bleached mixed hardwood pulp (commercial grade): 60%, bleached northernsoftwood kraft pulp (commercial grade): 20%; filler (precipitatedcalcium carbonate): 20%; starch: 0.5%; Hercon size 79AKD (0.5%): 0.2%,and Nalco 7520 retention aid (0.1%): 0.05%.

[0113] Hardwood and softwood kraft pulp laps are mixed in a hydrapulperand refined at 3.71% consistency to 470 ml CSF level. Filler and starchare added to machine chest. The Sizing agent and retention aid aremetered into the machine chest.

[0114] The results are presented in Tables 8, 9, 10, and 11. TABLE 8Test results of paper made in pilot paper machine. Printing ScatteringAbsorption Gurley Sample Grammage Density Brightness Opacity coefficientcoefficient porosity ID (g/m²) (kg/m³) (%) (%) (kg/m²) (kg/m²) (sec/100ml) wood 80.4 698 87.4 89.8 67.6 0.17 7.1 pulp cornstalk 76.9 784 88.787.2 59.5 0.14 171 pulp

[0115] Table 8 shows that the density of cornstalk pulp was higher thanthose of wood pulp. Brightness of cornstalk pulp is nearly 1 pointhigher than wood pulp, but the printing opacity is more than 2 pointslower. Both scattering coefficient and absorption coefficient for woodpulp were slightly higher than cornstalk pulp. Scattering coefficient isinversely related to paper bonding property. Porosity for cornstalk pulpis 171 sec/100 ml compared to 7.1 sec/100 ml for wood pulp. That meanswood pulp result in much more porous structure than cornstalk pulp.TABLE 9 Test results of paper made in pilot paper machine ScatteringAbsorption Sample Brightness Opacity coefficient coefficient CIE ID (%)(%) (kg/m²) (kg/m²) L A b L* a* b* Whiteness CIE Tint wood 87.35 91.1464.16 0.17 95.21 0.11 2.96 96.26 0.05 3.00 77.27 −1.96 pulp cornstalk88.63 88.95 58.01 0.15 95.29 0.25 2.09 96.33 0.19 2.14 81.35 −1.66 pulp

[0116] Table-9 shows that CIE Whiteness of cornstalk pulp was about 4points higher than wood pulp and CIE Tint was lower than wood pulp.Brightness, opacity, scattering coefficient, absorption coefficient ofcornstalk pulp and wood pulp were similar. LL* that represents lightnessincreasing from zero for black to 100 for perfect white, is similar forboth cornstalk pulp and wood pulp; a,a* that represents redness whenplus, is higher for cornstalk pulp than wood pulp; b,b* that representsyellowness when plus, is higher for wood pulp than cornstalk pulp. TABLE10 Test results of paper made in pilot paper machine Tensile TensileTearing Tearing Filler strength index Stretch TEA strength Index ContextSample ID (kN/m) (kN-m/g) (%) (J/m²) (mN) (mN-m²) (%) wood MD 2.150.0267 0.74  9.53 308 3.8 17% pulp CD 0.87 0.0120 1.73 11.56 379 4.7Cornstalk MD 3.25 0.0423 1.10 21.84 451 5.9 22% pulp CD 1.94 0.0255 2.6537.02 494 6.4

[0117] Table-10 shows the comparison of strength properties of wood pulpand cornstalk pulp both in machine-direction (MD) and cross-direction(CD). All of the strength properties of cornstalk pulp are 40% to 300%higher than that of wood pulp. Tensile strength properties of cornstalkpulp in machine direction was about 50% higher, and in cross-directionis 122% higher than those of wood pulp. Stretch value of cornstalk pulpin MD and CD directions were respectively 50% and 100% higher than thoseof hardwood pulp. TEA (tensile energy absorption) value of cornstalkpulp in MD direction is 130% and in CD direction is 200% higher thanthose of hardwood pulp. Similarly tear index of cornstalk pulp in MDdirection is 55% higher and CD direction is 36% higher than those ofhardwood pulp. Filler, in general, are responsible for weak bondingproperties of paper. Although cornstalk pulp retained 22% fillercompared to 17% filler in wood pulp, cornstalk pulp was much strongerthan wood pulp. Pilot paper machine trial has further demonstrated thatcornstalk pulp can hold the filler in the fiber matrix more efficientlythan does wood pulp. TABLE 11 Test results of paper made in Pilot papermachine Sheffield Burst Burst Taber Log 10 Smoothness Strength IndexStiffness Number of MIT Folding Sample ID (SU) (kPa) (kPa-m²/g) (g-cm)Double Folds Endurance wood pulp MD 1.70  23*  1.34* CD 0.71  8*  0.88*Felt 155 64.5 0.80 Wire 160 63.4 0.79 Cornstalk pulp MD 1.63 41 1.60 CD0.91 19 1.27 Felt 157 134 1.74 Wire 143 134 1.74

[0118] Table 11 shows the Sheffield smoothness, burst index, Taberstiffness and number of double folds of both cornstalk and hardwoodpulp. Sheffield smoothness of cornstalk pulp and hardwood pulp weresimilar in the felt direction, whereas in wire direction cornstalk pulpwas more smooth than hardwood pulp. Burst strength of cornstalk pulp wasmore than 100% stronger than hardwood pulp. Number of double folds forcornstalk pulp in MD and CD directions are respectively 41 and 19compared to 23* and 8* for wood pulp. Since wood pulp is too weak tofold under 1 kg tension, 0.5 kg tension was applied. 8* is actuallyequivalent to 1 number of fold and 23* is equivalent to only 8 number offold, if measured under 1 kg tension.

[0119] Paper machine trial has clearly demonstrated that cornstalk paperprepared under identical condition as hardwood paper, is much superiorin terms of strength properties than that of hardwood paper, and similarto each other in terms of optical properties.

[0120] It is understandable that various details of the invention mightbe changed without deviating from the scope of this invention. Moreover,the above-mentioned descriptions in various examples are for the purposeof illustration only, not for the purpose of limitation. Variousmodifications can be made in the present invention without departingfrom the spirit or scope of the invention. Thus, it is intended that thepresent invention cover the modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents.

What is claimed is:
 1. A method for producing pulp from agriculturalresidues, comprising: harvesting a portion of a cornstalk plant, whereinthe harvesting includes removing a portion of the cornstalk below aboutat least one of a ear on the cornstalk plant; drying the cornstalkportions; chopping the cornstalk portions; washing of the choppedcornstalk portions; compacting the washed cornstalk portions in a screwfeeder to remove water; extracting pulp from the compacted cornstalkportions with an alkaline pulping solution at predetermined conditions;fiberizing the pulp; washing the pulp; and treating of the fiberized andwashed pulp with a bleaching solution, wherein the bleaching solutionremoves residual lignin and color for increasing the brightness togreater than about 70% ISO.
 2. The method of claim 1, wherein batchprocesses of at least one of trembling, stationary digester, and superbatch digester is utilized.
 3. The method of claim 1, wherein continuousprocessing of at least one of Pandia digester and Kymer digester areutilized.
 4. The method of claim 1, wherein the cooking of cornstalk inthe alkaline solution is done at a temperature ranging from about 120 to160° C. for about 30 min to 120 min.
 5. The method of claim 4, whereinthe alkaline solution comprises an alkaline hydroxide solution includingat least one of sodium hydroxide, potassium hydroxide, ammoniumhydroxide, and calcium hydroxide.
 6. The method of claim 4, wherein thealkaline solution further includes at least one of sodium carbonate andsodium bicarbonate.
 7. The method of claim 6, wherein the alkalinesolution further includes sodium hydroxide.
 8. The method of claim 7,wherein the alkaline solution further includes anthraquinone.
 9. Themethod of claim 7, wherein the sodium hydroxide has a concentration inthe range from about 2% to 18% active alkali and the anthraquinone has aconcentration in the range from about 0.0% to 0.5%.
 10. The method ofclaim 7, wherein a pretreatment step involving compacted cornstalkmaterial with cellulose protecting agents such as MgCl₂, CaCO₃ at atemperature between about 60 to about 100° C. for about 30 to about 60minutes might be used in order to protect the hemicellulose duringalkaline digestion of cornstalk.
 11. The method of claim 1, wherein thebleaching solution comprises chlorine dioxide.
 12. The method of claim1, wherein the treating of the fiberized and washed pulp with ableaching solution is performed at a temperature ranging from about 50to 100° C. for about 30 to 120 minutes.
 13. The method of claim 1,wherein the alkaline pulping solution includes a concentration rangingfrom about 1% to 3% sodium hydroxide.
 14. The method of claim 1, whereina chlorine dioxide-alkaline extraction-chlorine dioxide (DED) bleachingsequence raises the pulp brightness to about 80-85% ISO.
 15. The methodof claim 14, wherein after the DED sequence one of a hydrogen peroxidebleaching solution (P), ozone solution (Z) and oxygen solution (O) isused for raising the pulp brightness to about 86 to 95% ISO.
 16. Themethod of claim 15, wherein the chlorine dioxide bleaching solutioncomprises a dosage of chlorine dioxide equivalent to pulps' kappa factorranging from about 0.01 to 0.5.
 17. The method of claim 16, wherein thehydrogen peroxide bleaching solution comprises: hydrogen peroxide ofabout 1 to 3% of o. d. pulp weight;sodium hydroxide of about 1 to 3% ofo. d. pulp weight; sodium silicate of about 1 to 3% of o. d. pulpweight; magnesium sulfate of about 0.02 to 0.06% of o. d. pulp weight;and trace amounts of chealant
 18. The method of claim 17, furthercomprising: a bleaching stage to improve the brightness of cornstalkpulp, wherein the bleaching stage uses bleaching reagent, such as ozoneof about 0.05 to 5% (of o. d. pulp weight) and oxygen of about 0.1 to 2%(of o. d. pulp weight).
 19. A method for making paper out of pulp fromagricultural residue, comprising: refining pulp from agriculturalresidue; blending the pulp from agricultural residue; cleaning;screening; and rolling in the paper machine, wherein the pulp fromagricultural residue is cornstalk pulp.
 20. The method of claim 19,wherein the cornstalk pulp has freeness level of at least 250 ml orgreater.
 21. The method of claim 19, wherein the cornstalk pulp has akappa number in a range of about 7 to
 80. 22. The method of claim 19,wherein the cornstalk pulp has a kappa number in a range of about 2 to7.
 23. The method of claim 19, wherein the cornstalk pulp has a kappanumber below about
 2. 24. The method of claim 19, wherein cornstalk pulpcan be used without refining and/or with refining to 250-500 ml CSFbefore combining with wood pulp to provide the specific properties thatcan meet the end-uses of paper products.
 25. The method of claim 19,wherein cornstalk pulp can be fractionated into long fiber and shortfiber fractions and reblended depending on the properties of end-uses tomaximize the performance of cornstalk pulp.
 26. The method of claim 19,wherein writing and printing paper, photocopy, specialty papers, andenvelope papers can be produced from bleached cornstalk pulp by theblending with one or more pulp and/or additives from a group comprising:bleached softwood chemical pulp; bleached hardwood chemical pulp: 0-20%;filler (precipitated or grounded calcium carbonate, clay, kaolin, talc,titanium dioxide, etc.): 0-30%; dry strength chemicals (starch or otherpolymeric materials): 0-4%; sizing agent (rosin emulsion, AKD, ASA orothers): 0.05-5%; and cationic and/or anionic polymeric retention aids(starch, poly acryl amide, poly ethylene imine, colloidal silica,bentonite, organic micro-particles, etc): 0-5%.
 27. The method, of claim19, wherein top white liner can be produced from bleached cornstalk pulpby blending with one or more additives from a group comprising: bleachedsoftwood chemical pulp: 0-30%; bleached hardwood chemical pulp: 0-30%;filler (precipitated or ground calcium carbonate, clay or kaolin):0-20%; dry strength agent (starch or other polymeric materials): 0-4%;sizing agent (rosin emulsion, AKD, ASA or others): 0.05-2%; andretention aid (starch, poly acryl amide, poly ethylene imine, colloidalsilica, bentonite, organic micro-particles, etc): 0-5%.
 28. The methodof claim 19, wherein carton package for milk, juice, and other beveragescan be produced from bleached cornstalk pulp by blending with one ormore additives from a group comprising: bleached softwood chemical pulp:0-20%; sizing agents (rosin emulsion, AKD, ASA or others): 0.01-5%; andretention aid (starch, poly acryl amide, poly ethylene imine, colloidalsilica, bentonite, organic micro-particles, etc): 0-5.5%.
 29. The methodof claim 19, wherein linerboard can be produced from unbleachedcornstalk chemical or semi-chemical pulp without or with unbleachedsoftwood chemical or semi-chemical pulp.
 30. The method of claim 19,wherein corrugating medium can be produced from high yield cornstalkpulp mixed with high yield hardwood pulp.
 31. The method of claim 19,wherein tissue papers, wet strength papers, and industrial papers can beproduced from bleached cornstalk pulp by blending with one or moreadditives from a group comprising: bleached softwood chemical pulp:0-30%; bleached hardwood chemical pulp: 0-20%; sizing agents (rosinemulsion, AKD, ASA or others): 0.01-5%; and retention aid (starch, polyacryl amide, poly ethylene imine, colloidal silica, bentonite, organicmicro-particles, etc): 0-5.5%.
 32. The method of claim 19, whereinphotocopy papers, specialty papers, and envelope papers can be producedfrom bleached cornstalk pulp by blending with one or more additives froma group comprising: bleached softwood chemical pulp: 0-30%; bleachedhardwood chemical pulp: 0-20%; filler (precipitated or ground calciumcarbonate, clay or kaolin): 0-40%; dry strength agent (starch or otherpolymeric materials): 0-5%; sizing agents (rosin emulsion, AKD, ASA orothers): 0.01-5%; and retention aid (starch, poly acryl amide, polyethylene imine, colloidal silica, bentonite, organic micro-particles,etc): 0-5.5%.